The proposal to replace hundreds of contractors within six months of passage of the bill ran into resistance from the State Department, which contends the federal government lacks enough trained specialists to take the place of private contractors who are protecting U.S. diplomats.

“Mercenary armies can overthrow a democracy,” said Filner as he joined other lawmakers to promote the bill, introduced Wednesday by Rep. Jan Schakowsky, D-Ill.

“We are going to fight Blackwater until there are no mercenaries,” said Filner, who also is battling the company's plans to build a West Coast training facility in Potrero.

The Schakowsky bill is the latest of several proposals to regulate, limit or end the activities of tens of thousands of private security operators who protect U.S. government employees, employees of private firms and other organizations in Iraq, Afghanistan and other conflict zones.

Sen. Bernie Sanders, I-Vt., is introducing a similar bill in the Senate.

State Department spokesman Karl Duckworth declined to comment on the legislation. But he noted that last month, Ambassador Patrick F. Kennedy said the State Department lacked enough guards to replace the contractors. Kennedy added that the Pentagon did not consider it “feasible or desirable” to take on the responsibility.

Schakowsky insisted it was possible to replace the contractors with government employees, either through training new guards or recruiting some of the current private contractors.

Blackwater has come under hightnened scrutiny since Sept. 16, when one of its convoys opened fire in Baghdad, killing 17 Iraqi civilians. The Iraqi government demanded the company be expelled from the country. Blackwater said its guards were acting in self defense after coming under attack while guarding State Department personnel.

Blackwater did not respond to a request for reaction to the legislation.

Private security contractors in Iraq have been criticized for being unaccountable, since they are exempt from prosecution by the Iraqi government. No security contractor has been prosecuted under U.S. law despite several accusations of wrongdoing.